1. Field of the Invention
This invention generally relates to a portable electro-optical reader in a system for reading indicia of varying light reflectivity and, in particular, to a compact bar code symbol reader mounted on an index finger of a user such that the natural pointing direction of the index finger aims the reader and, more particularly, to a finger-mounted reader that communicates with other system components by a low power, wireless, radio frequency, communications protocol.
2. Description of the Related Art
Various electro-optical readers and systems have been developed heretofore for reading indicia such as bar code symbols appearing on a label or on a surface of an article. In its simplest form, the symbol itself is a coded pattern of indicia comprised of, for example, a series of bars of various widths spaced apart from one another to bound spaces of various widths, the bars and spaces having different light reflecting characteristics.
The scanning of bar code patterns has become more complex as bar code patterns have become both more complex and more compact. The typical bar code pattern includes lines and spaces of different widths extending in an x direction, and can be scanned by one or more linear scans in the x direction. Moreover, because the direction of the scan is not always precisely aligned with the direction of the bar code pattern, more complex omnidirectional scanning patterns are sometimes used, wherein consecutive scan lines are angularly displaced relative to one another to form a complex omnidirectional scanning pattern. Two dimensional (2D) bar code patterns (Code 49) have also been introduced wherein, in addition to a typical bar code pattern having lines and spaces of varying widths along an x direction, typical bar code patterns are stacked one upon the other in the y direction to form the 2D bar code pattern. Accordingly, scanning of a 2D bar code pattern is more complex, and requires a raster type of scan wherein consecutive x direction scans are displaced in the y direction by the spacing between stacked rows of the 2D bar code pattern to form a raster scan.
The readers and scanning systems electro-optically transform the graphic indicia into electrical signals, which are decoded into alphanumerical characters that are intended to be descriptive of the article or some characteristic thereof. Such characters are typically represented in digital form and utilized as an input to a data processing system for applications in point-of-sale processing, inventory control, and the like. Scanning systems of this general type have been disclosed, for example, in U.S. Pat. Nos. 4,251,798; 4,369,361; 4,387,297; 4,409,470; 4,760,248; and 4,896,026, all of which have been commonly assigned to the same assignee as the present application.
As disclosed in some of the above patents, one embodiment of such a scanning system resides, inter alia, in a portable laser scanner which is grasped and hand-held by a user, which is designed to allow the user to aim the scanner, and more particularly, a light beam emanating therefrom, at a target bar code symbol to be read.
In prior art bar code scanners, the light source in a laser scanner is typically a gas laser or semiconductor laser. The use of a semiconductor device such as a laser diode as the light source in scanning systems is especially desirable because of its small size, low cost and low power requirements. The laser beam is optically modified, typically by a lens, to form a beam spot of a certain size at the target distance. It is preferred that the beam spot size at the target distance be approximately the same as the minimum width between regions of different light reflectivity, i.e., the bars and spaces of the symbol.
Bar code symbols are formed from bars or elements that are typically rectangular in shape with a variety of possible widths. The specific arrangement of elements defines the character represented according to a set of rules and definitions specified by the code or xe2x80x9csymbologyxe2x80x9d used. The relative size of the bars and spaces is determined by the type of coding used, as is the actual size of the bars and spaces. The number of characters per inch represented by the bar code symbol is referred to as the density of the symbol. To encode a desired sequence of characters, a collection of element arrangements are concatenated together to form the complete bar code symbol, with each character of the message being represented by its own corresponding group of elements. In some symbologies a unique xe2x80x9cstartxe2x80x9d and xe2x80x9cstopxe2x80x9d character is used to indicate where the bar code begins and ends. A number of different bar code symbologies exist. These symbologies include UPC/EAN, Code 39, Code 128, Codabar, and Interleaved 2 of 5.
For the purpose of this discussion, characters recognized and defined by a symbology shall be referred to as legitimate characters, while characters not recognized and defined by that symbology are referred to as illegitimate characters. Thus, an arrangement of elements not decodable by a given symbology corresponds to an illegitimate character(s) for that symbology.
In order to increase the amount of data that can be represented or stored on a given amount of surface area, several new bar code symbologies have recently been developed. One of these new code standards, Code 49, introduces a xe2x80x9ctwo-dimensionalxe2x80x9d concept by stacking rows of characters vertically instead of extending the bars horizontally. That is, there are several rows of bar and space patterns, instead of only one row. The structure of Code 49 is described in U.S. Pat. No. 4,794,239, which is hereby incorporated by reference.
A one-dimensional single-line scan, as ordinarily provided by hand-held readers, has disadvantages in reading these two-dimensional bar codes; that is, the reader must be aimed at each row individually. Likewise, the multiple-scan-line readers produce a number of scan lines at an angle to one another so these are not suitable for recognizing a Code 49 type of two-dimensional symbols.
In the scanning systems known in the prior art, the light beam is directed by a lens or similar optical components along a light path toward a target that includes a bar code symbol on the surface. The scanning functions by repetitively scanning the light beam in a line or series of lines across the symbol. The scanning component may either sweep the beam spot across the symbol and trace a scan line across and past the symbol, or scan the field of view of the scanner, or both.
Scanning systems also include a sensor or photodetector which functions to detect light reflected from the symbol. The photodetector is therefore positioned in the scanner or in an optical path in which it has a field of view which extends across and slightly past the symbol. A portion of the reflected light which is reflected by the symbol is detected and converted into an electrical signal, and electronic circuitry or software decodes the electrical signal into a digital representation of the data represented by the symbol that has been scanned. For example, the analog electrical signal from the photodetector may typically be converted into a pulse width modulated digital signal, with the widths corresponding to the physical widths of the bars and spaces. Such a signal is then decoded according to the specific symbology into a binary representation of the data encoded in the symbol and to the alphanumeric characters represented thereby.
The decoding process in known scanning system usually works in the following manner. The decoder receives the pulse width modulated digital signal from the scanner, and an algorithm implemented in software attempts to decode the scan. If the start and stop characters and the characters between them in the scan are decoded successfully and completely, the decoding process terminates and an indicator of a successful read (such as a green light and/or an audible beep) is provided to the user. Otherwise the decoder receives the next scan, performs another decode attempt on that scan, and so on, until a completely decoded scan is achieved or no more scans are available.
Such a signal is then decoded according to the specific symbology into a binary representation of the data encoded in the symbol, and to the alphanumeric characters so represented.
Laser scanners are not the only type of optical instrument capable of reading bar code symbols. Another type of bar code reader incorporates detectors based upon charge coupled device (CCD) technology. In such readers, the size of the detector is larger than or substantially the same as the symbol to be read. The entire symbol is flooded with light from the reader, and each CCD cell is sequentially read out to determine the presence of a bar or a space. Such readers are lightweight and easy to use, but require substantially direct contact or placement of the reader on the symbol to enable the symbol to be properly read. Such physical contact of the reader with the symbol is a preferred mode of operation for some applications, or is a matter of personal preference by the user.
Accordingly, it is a primary object of the present invention to provide a compact bar code reader mounted on an index finger of an operator such that the natural pointing direction of the index finger aims the reader.
Another object of this invention is to enable the finger-mounted reader to communicate with a remote host by a low power, wireless, radio frequency protocol to minimize power usage onboard the reader.
A further object of the subject invention is the provision of a compact bar code scanning arrangement which is simple, is capable of producing several different types of scanning patterns, and is capable of achieving high scanning rates.
The present invention provides a compact bar code scanner which in different embodiments is capable of scanning in any one of several modes, a linear scan mode in which it scans along a single axis, an omnidirectional scan mode in which it scans with consecutive scan lines which are angularly displaced relative to each other in an omnidirectional scan pattern, such as a Lissajous scan pattern, or a raster scan mode in which it scans with consecutive scan lines along a first scan axis, and the consecutive scan lines are displaced relative to each other along a second perpendicular axis.
In accordance with this invention, one feature resides, briefly stated, in a reader for, and a method of, electro-optically reading coded indicia having parts of different light reflectivity, comprising a portable housing supportable on a finger of a user, and aimable by movement of the finger at an indicium to be read. A scan engine is supported by the housing and includes a scanner for scanning the indicium, and a decoder for generating a decoded, digital, data signal representing the indicium. A radio frequency transmitter is supported by the housing and is operative for transmitting the decoded, digital, data signal to a host remote from the reader by a low power, wireless, radio frequency, communications protocol.
In the preferred embodiment, the housing includes a light-transmissive window aimable by the finger movement at the indicium. The scan engine includes a source for directing a light beam through the window at the indicium for reflection therefrom, and a detector having a field of view and operative for detecting light reflected from the indicium and entering the housing through the window, and for generating an electrical analog signal corresponding to the indicium. The scanner is operative for scanning at least one of the light beam and the field of view in a scan over the indicium.
The transmitter may be activated by the host to initiate transmission. The transmitter transmits successive decoded, digital, data signals in time periods spaced timewise apart. A suitable wireless protocol is known as Bluetooth, Version 1.0, the specification of which can be found on the Internet at http:/www.bluetooth.com. This protocol utilizes little electrical energy, and conserves battery life.
According to another aspect of the present invention, the host is operative for receiving and processing the decoded, digital, data signal transmitted by the transmitter, and for generating an acknowledgment signal. An auditory annunciator is spaced apart from the reader and the host and is in wireless, radio frequency, communication with the host, for receiving the acknowledgment signal and, upon receipt thereof, for producing an acknowledgment sound audible to the user and indicative that the host received the decoded, digital, data signal. The annunciator is preferably worn by the user, for example, by being clipped on the user""s clothing, or by being suspended from a neck strap.
The reader may, but need not, incorporate a scanner in which the light beam scans the indicia to be read. Alternatively, the light beam may be merely illuminating; in that case, the light detector may preferably be a CCD detector.
In a preferred embodiment, the reader incorporates or forms part of a ring which is desirably worn on an index finger of the user. To scan the indicia, the user points his or her index finger in the relevant direction. In some embodiments, an automatic scanning mechanism may be incorporated within the reader, so that the emitted beam automatically scans back and forth across the indicia (either in a two-dimensional scan or in a one-dimensional scan) even when the reader is held stationary. In other embodiments, however, no automatic scanning mechanism is provided, and the emitted light beam emerges in a fixed direction from the reader. In those embodiments, the user scans the beam across the indicia to be read by manually moving the reader, typically by moving his or her arm back and forth or by a twisting movement of the wrist.
Switching means may be provided for actuating the reader. Preferably, these may comprise a switch or button, attached to or forming part of the ring or part of a housing secured to the ring, whereby the user can operate the device merely by pressing the button with his or her thumb. This is particularly convenient when the reader is arranged to be worn on the index finger. Alternatively, a pull-cord may be provided which is secured to a second ring, arranged to be worn on a finger of the user""s hand adjacent to the finger which is wearing the reader. By a suitable movement of the fingers, for example by flexing the second finger, the cord is pulled, thereby operating the device.
It will of course be understood that there are many other possibilities for actuating the device, including switch mechanisms which operate under voice control, and mechanisms which determine when the user""s hand is being moved in a scanning motion.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.